1. Field of the Invention
The invention relates to a physiological signal measuring tool, and more particularly to a physiological signal collection unit and a detector that are adapted for use on an anatomical part covered with hair.
2. Description of the Related Art
Current applications of physiological signal collection units for the head, such as photoplethysmography (PPG) measurement, oxyhemoglobin and deoxyhemoglobin measurement of the brain, and regional cerebral oxygen saturation (rSO2) measurement of the brain, could be used to analyze blood flow of the brain. Technically, the current applications use lighting components (such as light emitting diodes) to illuminate the anatomical part of a test subject, and use light sensing components (such as phototransistors or photodiodes) to receive light reflected or transmitted from the anatomical part to proceed with signal processing and analysis.
However, the scalp is covered with hair, so that when proceeding with the PPG measurement of the brain, hemoglobin and rSO2 detection of the brain, both emission and reception of the light will be interfered by hair to cause scattering that affects intensity, resulting in inability to obtain a correct physiological signal. Most of current improvements in the relevant field involve increasing the power of the lighting devices to ensure the intensity of the received light. However, illumination using high power light may result in temperature variations of the skin tissue and cause vasodilation that affects blood flow, or even damage to skin and brain tissues. On the other hand, power consumption and effect of hair denseness on the reflected light intensity are also problems.
In addition, an electroencephalogram (EEG) measuring apparatus includes an EEG cap and a plurality of electrodes to measure EEG. To ensure the signal transmission, conductive adhesive must be used on each contact between the electrodes and the scalp. However, the process of wearing the current EEG measuring apparatus is complicated and the hair of the test subject must be washed to remove the conductive adhesive after finishing with the measurement.